This invention relates generally to medical devices and more specifically to intervertebral disk stabilization systems and methods of stabilizing the spine of living beings.
This application claims priority on Brazilian Patent Application, Ser. No. 9805340-0, filed on Dec. 14, 1998, entitled VARIABLE EXPANSION INSERT FOR STABILIZING THE VERTEBRAL COLUMN, whose disclosure is incorporated by reference herein.
Numerous types of devices or systems are available for the fixation of the vertebral column of living beings. For example, some devices are prostheses, e.g., plates or other structures, formed of rigid materials of fixed sizes and volumes capable of being fastened, e.g., bolted, to the bony structure of vertebral column anteriorly and/or posteriorly through bores excavated in those vertebrae involved. The fasteners used in such devices or systems are commonly referred to as cortical bolts or medullary bolts, depending upon the type of thread of the bolt. In some systems or devices parts of human bone from the patient himself/herself, or from bone banks or dehydrated human bone is used to aid in securing the prosthesis to the bony structure(s) of the vertebrae. One of the greatest drawbacks of such prior art devices or systems are that they are difficult to use. In this regard, the deployment and mounting of a bolt-based fixation device is delayed by the necessity to bore the bony structures of the vertebrae for receipt of the securement bolts. Moreover, the location of the bore holes for those bolts must be precisely located and oriented to match up with the pre-established holes in the plates or other support structures forming the remainder of the device or system. Another drawback of such spine fixation devices is the fact that they typically take up such substantial space in the body when secured in place, that they may result in the formation of traumatic lesions to adjacent anatomic structures. Lastly, traction exerted by movement of the patient, may cause partial or total detachment of one or more of the bone fixation bolts, which action may also result in the formation of traumatic lesions to adjacent anatomic structures and/or instability of part or all of the fixation system.
Various patents and printed patent literature have also disclosed devices and systems for fixation or stabilization of the spine or vertebral column of a living being. See for example, U.S. Pat. Nos.: 4,863,476 (Shepperd), 5,591,235 (EKuslich), 5,653,761 (Pisharodi), 5,653,762 (Pisharodi), 5,653,763 (Errico et al.), 5,693,100 (Pisharodi), 5,713,904 (Errico et al.), 5,782,832 (Larsen et al.), 5,865,847 (Kohrs et al.), and 5,865,848 (Baker), PCT Application Publication Nos.: WO 90/00037, WO 95/31158, WO 97/06753, and WO 98/10722, European Patent Application Nos.: 0 599 766 A1, and 0 635 246 A1, Spanish Patent No. ES 2 099 008, and Russian Patent No.: 2063730.
While the spine stabilization or fixation devices of the patent literature may be generally suitable for their intended purposes, they still leave much to be desired from the standpoints of ease of use and effectiveness. For example, some prior art spine fixation devices require excision of the anterior and/or posterior longitudinal ligaments, thereby destabilizing the spine. Thus, these systems require some mechanical means to fuse or fix the adjacent vertebrae to each other, e.g., removal or drilling of the bone to secure the device in position with respect to each vertebra with some type of mechanical bridge therebetween. Other types of fixation devices make use of hollow or apertured implants designed to be packed with bone chips or particles and placed into excavations through the exterior, hard cortical bone, into the soft interior cancellous bone of opposed vertebrae to facilitate the ingrowth of bone into the implant and thus fuse the two vertebrae together. This type of fixation device may be prone to damage the immediately adjacent vertebrae due to compressive forces thereon.
While some prior art devices don""t require excision of the ligaments to effect spine stabilization, they, nevertheless, typically require the partial or complete extraction and removal of the disk in order to place them into the intervertebral space, where such devices seek to replace the function of the disk (albeit less than optimally).
Notwithstanding all of the prior art now in existence, a need still exists for a spine stabilization system which is easy to use, effective, and safe.
It is a general object of this invention to provide a vertebral-column stabilizing device and deployment system which overcomes the disadvantages of the prior art and addresses those needs.
It is another object of this invention to provide a device and system for deploying it in the intervertebral space between a superior and inferior vertebra of a living being to stabilize the spine.
It is another object of this invention to provide a device for deployment in the intervertebral space between a superior and inferior vertebra of a living being to stabilize the spine, yet which does not require the excision of either the anterior or posterior longitudinal ligament.
It is another object of this invention to provide a device and system for deploying it to stabilize the spine of a living being without requiring removal of bone.
It is another object of this invention to provide a device and system for deploying it to stabilize the spine of a living being without interruption or removal of bone growth surfaces.
It is another object of this invention to provide a device for deployment in the intervertebral space between a superior and inferior vertebra of a living being to stabilize the spine, yet which does not require the complete removal of the interposed disk, e.g., in all it requires is the creation of a small opening in the annulus of the disk through which the nucleus or portion thereof is excised.
It is another object of this invention to provide a device and system for deploying it in the intervertebral space between a superior and inferior vertebra of a living being, so that when the device is deployed it effectively stabilizes the spine.
It is another object of this invention to provide an adjustable and controllable spine stabilization device and system for deploying it in the intervertebral space between adjacent vertebra to establish a desired lordotic curvature of the spine.
It is another object of this invention to provide a spine stabilization device and system for deploying it in the intervertebral space between a superior and inferior vertebra which is easy to use, and minimally invasive.
It is another object of this invention to provide an expandable vertebral-column stabilizing device which is simple in construction.
It is another object of this invention to provide a deployment system which is simple in construction and easy to use to deploy an expandable vertebral-column stabilizing device.
A system for stabilizing the vertebral column of a living being. The system includes a variable expansion device and a deployment system for deploying the device. When deployed the device stabilizes a superior vertebra and immediately adjacent inferior vertebra of the vertebral column, without requiring the excision of bone from the superior or inferior vertebrae or the resection of the adjacent anterior or posterior longitudinal ligaments.
The stabilizing device basically comprises an expandable insert and an expansion insert. The expandable insert comprises a hollow cylindrical body having a longitudinal axis, an proximal end portion and a distal end portion. The proximal end portion has a pair of slots extending therethrough generally parallel to the longitudinal axis of the expandable insert. The slots extend partially into the distal end portion of the expandable insert. The distal end portion and at least a portion of the proximal end portion of the expandable insert have an outer surface about which an external, helical, self-tapping thread extends. The distal end portion and the at least a portion of the proximal end portion of the expandable insert are of a sufficient size to be screwed into the intervertebral space between the superior and inferior vertebrae, to an operative position and orientation. In the operative position and orientation the expandable insert is located at a desired depth within the intervertebral space and its slots are oriented in a plane generally perpendicular to the portion of the longitudinal axis of the being""s vertebral column between the superior and inferior vertebrae.
The self-tapping thread of the expandable insert is a sufficient height to cut into the cortical bone of the superior and inferior vertebrae contiguous to the intervertebral space, but not substantially into the cancellous bone.
The proximal end portion of the expandable insert has an internally threaded, e.g., fine threaded, bore extending through it and into and through at least a portion of the distal end portion of the expandable insert. The internally threaded bore communicates with the slots in the expandable insert.
The expansion insert has an externally threaded outer surface and is arranged to be screwed into the internally threaded bore in the proximal end portion of the expandable insert when the expandable insert is in the desired position and orientation. In a preferred embodiment the outer surface of the expansion insert is tapered from the proximal end to the distal end. Thus, when the expansion insert is screwed into the threaded bore in the expandable insert, it causes the slots to open and thereby spread the superior and inferior vertebrae apart, thereby stabilizing the being""s vertebral column.
The deployment system in the preferred embodiment comprises two tools which are arranged to cooperate with each other. A first one of the tools has portion, e.g., an elongated hollow shaft having a pair of extending fingers, adapted to fit into at least one of the slots in the expansion insert to enable the tool to screw the expandable insert to the desired depth and orientation in the intervertebral space between the superior and inferior vertebrae and to hold it in the desired orientation at that depth. The second tool, e.g., an elongated rod-like shaft arranged to extend through the hollow interior of the first tool, has a working end, e.g., a square head, adapted to engage a portion, e.g., a square slot, of the expansion insert to screw the expansion into the threaded bore in the proximal end portion of the expandable insert to cause the slots to spread apart, whereupon the device stabilizes the being""s vertebral column.